Driving motor, especially for a pump

ABSTRACT

Described is a drive motor, in particular for a pump, which has a rotor having a drive shaft, and a stator enclosed by a stator casing which is enclosed by an outer casing. The stator casing and the outer casing form an intermediate space which is hermetically sealingly closed off and which is filled with a cooling fluid. The cooling fluid is positively moved by means of a coolant impeller. For that purpose the coolant impeller is coupled to the drive shaft of the electric drive motor by means of a permanent magnet coupling which is in the form of a synchronous coupling, a hysteresis coupling or an eddy current coupling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing of PCT/DE03/01462 filed May7, 2003, claiming priority to DE 102 20 477.2 filed May 7, 2002 and DE103 17 492.3 filed Apr. 16, 2003.

TECHNICAL FIELD

The invention is directed to a drive motor, in particular for a pump.

BACKGROUND OF THE INVENTION

In pumps the medium to be conveyed, that is to say to be pumped, isusually employed directly as a coolant for the drive motor of the pump.When dealing with sewage or waste water or other contaminated fluidsthat can result in blockage of the cooling volume of the drive motor. Inaddition pumps and in particular sewage pumps are known, which have aninternal cooling system for their drive motor. In such an arrangementcirculation of the coolant is effected by an additional small coolantimpeller. That coolant impeller can be operatively connected to its ownsmall electric motor. Another possible option involves driving theabove-mentioned small coolant impeller directly by the pump drive motor.In that case either the coolant impeller is provided at the free end ofthe drive shaft of the drive motor, associated with the pump impeller,or the drive shaft of the drive motor is prolonged on the side remotefrom the free shaft end thereof and the coolant impeller is disposed onthe side of the drive motor, which is remote from the pump impeller. Inthose known pumps, irrespective of the respective arrangement of thecoolant impeller, it is necessary for the coolant circuit to be sealedoff in relation to the drive motor and possibly the medium beingconveyed, that is to say sewage, by means of dynamic seals. Dynamicseals however are subject to leakage which cannot be reliably excluded.Such leakage results for example in the danger that, in the extremecase, the cooling system fails or coolant penetrates into the drivemotor.

CH 614 760 A5 discloses a canned centrifugal pump having a magneticcoupling whose outer part which surrounds the can and whose inner partwhich is surrounded by the can are provided with bar-shaped permanentmagnets which are disposed in axis-parallel mutually juxtaposedrelationship. The pump casing, the rotor of the canned centrifugal pumpand the inner coupling part of the magnetic coupling preferably comprisea temperature-resistant and/or acid-resistant plastic material in orderto provide a powerful, gland-less chemical canned centrifugal pump whichmakes it possible to achieve operationally reliable protection fromcorrosion. The side faces and the end faces of the permanent magnetswhich are completely embedded in the inner coupling part convergeoutwardly. Bearing substances are embedded in the plastic material, inthe region of the bearing surfaces of the interconnected parts of themagnetic coupling. In that known canned centrifugal pump the permanentmagnet coupling serves for mechanically coupling the pump drive motor tothe pump impeller.

A canned centrifugal pump with a permanent magnet coupling is also knownfor example from DE 33 37 086 C2. That known centrifugal pump with amagnetic coupling has a can cup of plastic material which has areinforcement at least in its axial can region. The can cup of plasticmaterial is enclosed from the outside by a cup-shaped jacket ofhigh-quality steel which serves as a shape stabiliser and holder for thecan. In this case also the permanent magnet coupling is provided forconnecting the pump drive motor to the pump impeller, in which respect,even at higher pressures and temperatures of the respective medium beingconveyed, the can cup of plastic material is of maximum possiblestability and good heat dissipation out of the region of the can cup ispossible.

DE 36 39 719 C3 describes a canned magnetic pump with a pump casing, apump impeller and a magnetic coupling having an outer drive part and aninner rotary part magnetically coupled thereto, wherein the outer drivepart and the inner rotary part are hermetically sealed from each otherby a can cup. A partial flow of the delivery flow of the canned motorpump, which is branched from that delivery flow and which serves tolubricate the pump plain bearings and possibly for dissipating heatlosses from the magnetic coupling and bearing heat, is passed throughthe interior of the can cup. The end, near the pump, of the tube-likepart of the can cup has a connecting flange which projects away from theaxis of rotation of the magnetic coupling and with which it is fixed tothe pump casing. The can cup can be subjected to the action of a heatingmeans which is independent of the medium being conveyed, in order toprovide a canned magnetic pump which, while being relatively simple toproduce, enjoys a relatively wide range of uses both at high and also atlower temperatures of the medium being conveyed, wherein the can cupaffords an enhanced level of security in an accident or damagesituation. For that purpose, in that known canned magnetic pump, atleast the tube-like part of the can cup is of an at least double-wallconfiguration and is formed by at least two can walls which are arrangedconcentrically relative to each other and relative to the axis ofrotation of the magnetic coupling. The internal wall space formed by thedouble or multiple wall structure serves to receive a heating or coolingagent. Provided in the connecting flange which is mechanically firmlyand sealingly connected to the can walls are at least one feed passageleading to the internal wall space and at least one discharge passagefor the heating agent or coolant. In this known canned magnetic pump themagnetic coupling also serves for operatively connecting the drive motorthereof to the pump impeller.

DE 43 19 619 A1 discloses a submersible motor-driven pump with anelectric drive motor, under which is fixed the casing of a centrifugalpump, wherein the casing of the drive motor is coaxially surrounded onthe outside by a cooling jacket through which flows the medium to beconveyed. In this case therefore the medium to be conveyed, that is tosay to be pumped, is used as a coolant, which—as has been stated in theopening part of this specification—can result in blockage of the coolingjacket when dealing with sewage or waste water or other contaminatedfluids. Such a blockage can then lead to overheating of the drive motorand, in the extreme case, total failure thereof.

DE 44 34 461 A1 discloses a submersible motor-driven pump for heavilycontaminated fluids. In order to permit cleaning of deposits in theinterior of the pump, the submersible motor-driven pump which isprovided with a tangential pressure connection and a jacket space whichencloses the drive motor and through which the fluid being conveyedflows has a flushing connection which is arranged at the end of thejacket space, that is remote from the pump, the flushing connectionbeing connectable to an external fluid source. The flushing connectionis preferably provided with a releasably fixed closure cap provided witha vent system. That represents a structural complication and expenditurewhich is not to be disregarded.

A cooling unit for cooling submersible mud, sewage and sludgemotor-driven pumps for the purposes of dry installation is known from DE196 40 155 A1. That known cooling unit represents a separateconstruction without fixed structural connection to the submersiblemotor-driven pump.

DE 298 14 113 U1 discloses a permanent magnet coupling pump with a pumpunit having a rotor which is arranged in a can cup and which is coupledto a driver of a drive unit, which driver extends around the can cup andcan be driven in rotation by means of a drive motor. That knownpermanent magnet coupling pump has a cage which is connected at its oneend to the pump unit and which is connected at its opposite end to thedrive motor. The driver and the drive motor are drivingly connected byway of a drive means of a material which is a poor conductor of heat.The drive means can be in the form of a coupling or can have a couplingwhich is interposed into the drive shaft provided between the driver andthe drive motor. The coupling is in the form of a dog coupling, anelastomer coupling or a permanent magnet coupling.

The object of the present invention is to provide a drive motor inparticular for a pump, which has an internal cooling system which isstatically hermetically sealed off.

BRIEF SUMMARY OF THE INVENTION

That object is attained in accordance with the invention by the featuresof claim 1. Preferred configurations and developments of the drive motoraccording to the invention are characterised in the appendant claims.

The drive motor according to the invention has the advantage that itdoes not come directly into contact with the medium to be conveyed suchas sewage or waste water or another contaminated fluid so that the riskof the cooling system of the drive motor becoming blocked is eliminated.A further, quite considerable advantage is that dynamic seals areavoided, so that corresponding leakage effects are reliably excluded.With the drive motor according to the invention, the permanent magnetcoupling does not serve for coupling the drive shaft of the drive motorto the pump impeller but it serves for coupling the drive shaft of thedrive motor to the coolant impeller of the hermetically sealed coolingsystem of the electric drive motor.

The cooling system according to the invention can be used not only inrelation to pumps, in particular sewage and waste water pumps, but inrelation to any electric drive motor with a hermetically sealed coolingsystem. Instead of a pump impeller, it is therefore also possible toprovide or mount on the drive shaft of the electric drive motor, anyother per se known machine component such as a belt pulley, a V-beltpulley, a toothed belt pulley or the like.

Further details, features and advantages will be apparent from thedescription hereinafter of embodiments illustrated by way of example inthe drawing of a drive motor according to the invention for a pump, inparticular a sewage or waste water pump.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing:

FIG. 1 shows a view in longitudinal section of a first embodiment of apump with a permanent magnet coupling between the drive shaft of theelectric drive motor and the coolant impeller of the staticallyhermetically sealed cooling system of the drive motor, wherein thepermanent magnet coupling is in the form of a synchronous coupling withfirst and second permanent magnet devices,

FIG. 2 shows the upper portion of the drive motor of FIG. 1 on a largerscale for further improved illustration of the permanent magnet couplingin the form of a synchronous coupling,

FIG. 3 shows a view in longitudinal section similar to FIG. 1 of asecond embodiment of the drive motor of a pump, in particular a sewageor waste water pump, with another configuration of the permanent magnetcoupling formed by a synchronous coupling,

FIG. 4 is a view similar to FIG. 2 of the upper portion of the drivemotor shown in FIG. 3 on a larger scale for further improvedillustration of the permanent magnet coupling in the form of asynchronous coupling,

FIG. 5 shows a view in longitudinal section similar to FIGS. 1 and 3 ofa third embodiment of a pump, in particular a sewage or waste waterpump, with a permanent magnet coupling which is formed by a synchronouscoupling but which is provided on the drive shaft between the rotor ofthe drive motor and the pump impeller,

FIG. 6 shows the lower portion of FIG. 5 on a further enlarged scale forfurther improved illustration in particular of the synchronous coupling,

FIG. 7 is a view in longitudinal section similar to FIGS. 1, 3 and 5 ofa fourth embodiment of a pump with a permanent magnet coupling betweenthe coolant impeller and the drive shaft of the electric drive motor,the permanent magnet coupling being formed by a hysteresis coupling,

FIG. 8 shows the upper portion of FIG. 7 on an enlarged scale—similarlyto FIGS. 2, 4 and 6—for further illustrating the hysteresis coupling,

FIG. 9 is a view in longitudinal section similar to FIGS. 1, 3, 5 and 7of a fifth embodiment of a pump with a permanent magnet coupling formedby an eddy current coupling, and

FIG. 10 shows the upper portion of FIG. 9 on an enlarged scale forfurther improved illustration of the eddy current coupling between thedrive shaft of the electric drive motor and the coolant impeller of thehermetically sealed cooling system of the electric drive motor.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a view in longitudinal section of a pump 10 which inparticular is a sewage or waste water pump. The pump 10 has an electricdrive motor 12 with a stator 14 and a rotor 16. The winding ends of thestator winding of the stator 14 are denoted by reference 18. The rotor16 is non-rotatably connected to a drive shaft 20. The drive shaft 20has a front end portion 22 and a rear end portion 24 which project awayfrom each other out of the rotor 16.

The stator 14 of the electric drive motor 12 is sealingly enclosed by astator casing 26. The stator casing 26 has a cup-shaped main casingportion 28 and a front casing portion 30 sealingly connected thereto.

The drive shaft 20 of the electric drive motor 12 is dynamicallysupported with its rearward end portion 24 by means of a bearing element32 at the main casing portion 28 of the stator casing 26. The driveshaft 20 is also dynamically supported with its front end portion 22 bymeans of a bearing element 34 in the front casing portion 30 of thestator casing 26.

The stator casing 26 is enclosed by an outer casing 36 which is spacedfrom the stator casing 26 so that an intermediate space 38 is providedbetween the stator casing 26 and the outer casing 36. The intermediatespace 38 can be filled with a cooling fluid 42 through a filling opening40. After complete filling of the intermediate space 38 with the coolingfluid 42 the filling opening 40 is sealingly closed by means of aclosure element 44, thereby affording a hermetically sealed coolingsystem 46 for the electric drive motor 12. The cooling fluid 42 providedin the intermediate space 38 of the hermetically sealed cooling system46 is positively moved in operation of the electric drive motor 12, thatis to say during rotation of the rotor 16, by means of a coolantimpeller 48, in order to provide optimum cooling of the electric drivemotor 12.

The coolant impeller 48 is rotatably mounted on a shaft 50 and coupled,that is to say operatively connected, to the drive shaft 20 of theelectric drive motor 12 by means of a permanent magnet coupling 52.

As is in particular clearly visible also from FIG. 2, the permanentmagnet coupling 52 is in the form of a synchronous coupling 53comprising a first permanent magnet device 54 and a second permanentmagnet device 56 which are spaced from each other by a gap 58 in whichthere is provided a partition element 60. The partition element 60comprises a non-magnetisable material. The permanent magnet devices 54and 56 are of a flat-faced disk-shaped configuration and are axiallyspaced from each other in order to form the gap 58. The partitionelement 60 is in the form of a plate element 62 which is sealinglysecured to an annular collar 64 of the main casing portion 28 of thestator casing 26. For that purpose, the partition element 60 formed bythe plate element 62 is clamped in sealing relationship between theannular collar 64 of the main casing portion 28 of the stator casing 26and a cap element 66. The shaft 50 for the coolant impeller is fixedbetween the cap element 66 and the plate or partition element 60, 62.

The partition element 60 formed by the plate element 62 and the annularcollar 64 of the main casing portion 28 of the stator casing 26 form adry space portion 68 in which the first permanent magnet device 54 isprovided. The first permanent magnet device 54 is fixed to a carrier 70which is accurately positioned at the end of the rearward end portion 24of the drive shaft 20, that is to say it is accurately centrallypositioned and fixed in such a way as to avoid an unbalance.

As can be seen from FIG. 1, a pump impeller 72 is fixed to the front endportion 22 of the drive shaft 20.

In the embodiment of the drive motor shown in FIGS. 1 and 2 the firstpermanent magnet device 54 and the second permanent magnet device 56 areformed from face rotational coupling elements of a flat-faced, annulardisk configuration. In comparison, FIGS. 3 and 4 show a pump 10 with apermanent magnet coupling 52 between the drive shaft 20 of the electricdrive motor 12 and the coolant impeller 48, wherein the first permanentmagnet device 54 and the second permanent magnet device 56 are in theform of central coupling elements arranged in mutually concentricrelationship.

The annular first and the annular second permanent magnet devices 54 and56 are radially definedly spaced from each other so that between themthere is an annular gap 58 in which there is a partition element 60which is in the form of a cup.

In this embodiment also, the partition element 60 is sealingly clampedbetween the annular collar 64 of the main casing portion 28 of thestator casing 26 and a cap element 66, thus affording a dry spaceportion 68 in which the first permanent magnet device 54 is arranged.

Identical details are denoted in FIGS. 3 and 4 by the same references asin FIGS. 1 and 2 so that there is no need for all those features to bedescribed in detail once again, in connection with FIGS. 3 and 4.

FIGS. 5 and 6 show an embodiment of the drive motor of a pump in whichthe permanent magnet coupling 52 with the coolant impeller 48 isprovided not at the rear end portion 24 of the drive shaft 20 of theelectric drive motor 12—as in the embodiments of FIGS. 1 and 2 and FIGS.3 and 4 respectively—but at the front end portion 22 of the drive shaft20. In this embodiment also, the permanent magnet coupling 52 is in theform of a synchronous coupling 53 having a first permanent magnet device54 and a second permanent magnet device 56 which are spaced from eachother by an annular gap in which there is a partition element 60. Thefirst permanent magnet device 54 is fixed to the front end portion 22 ofthe drive shaft 20. The second permanent magnet device 56 is combinedwith or fixedly connected to a coolant impeller 48. The partitionelement 60 is in the form of a cylindrical sleeve 74 which is fixed tothe front casing portion 30 of the stator casing 26 in order to afford adry space portion 68.

In order further to improve the cooling of the cooling fluid 42 providedin hermetically sealed relationship in the intermediate space 38, acasing portion 76 of the pump 10 has cooling ribs 78 which project intothe intermediate space 38 which is hermetically sealed off and which isfilled with the cooling fluid 42. The cooling ribs 78 provide for anincrease in surface area and thus provide for optimum cooling of thecooling fluid 42.

The same features are identified in FIGS. 5 and 6 by the same referencesas in FIGS. 1 through 4, so that there is no need for all those featuresto be described once again, in connection with FIGS. 5 and 6.

FIGS. 7 and 8 show an embodiment of the drive motor of a pump, whichdiffers from the embodiment of the pump 10 shown in FIGS. 1 and 2 inthat the permanent magnet coupling 52 between the drive shaft 20 of theelectric drive motor 12 of the pump 10 and the coolant impeller 48 isnot in the form of a synchronous coupling but in the form of ahysteresis coupling 80 having a hysteresis surface element 82 and apermanent magnet device 84 which are spaced from each other by a gap 58in which there is provided a partition element 60 comprising anon-magnetisable material. The permanent magnet device 84 is combinedwith, that is to say fixedly connected to, the coolant impeller 48. Thehysteresis surface element 82 is fixedly connected to the drive shaft20. The hysteresis surface element 82 comprises a magnetic material ofrelatively high remanence and relatively low coercive field strength sothat magnetic reversal is possible against a relatively low resistance.While a synchronous coupling does not exhibit any slip, a hysteresiscoupling has a certain slip and consequently a power loss caused by thetransmission mechanism of the coupling.

Except for the permanent magnet coupling 52 the pumps 10 shown in FIGS.1 and 2 and FIGS. 7 and 8 are in principle of a similar configuration sothat there is no need for all features to be described in detail onceagain with reference to FIGS. 7 and 8.

FIGS. 9 and 10 show an embodiment of the drive motor of a pump 10similar to the pumps 10 shown in FIGS. 1 and 2 and shown in FIGS. 7 and8, wherein the pump 10 shown in FIGS. 9 and 10 has a permanent magnetcoupling 52 which is not formed either by a synchronous coupling (seeFIGS. 1 and 2) or by a hysteresis coupling (see FIGS. 7 and 8), but byan eddy current coupling 86 having an eddy current surface element 88and a permanent magnet device 90. The permanent magnet device 90 isfixedly connected to the coolant impeller 48. The eddy current surfaceelement 88 is fixed to the drive shaft 20 of the electric drive motor12. The eddy current surface element 88 comprises a surface element 92comprising an electrically conductive material such as copper or thelike and a surface element 94 comprising a soft-magnetic material, thoseelements being fixedly connected together, for example riveted. Moreoverthe pump shown in FIGS. 9 and 10 is of a similar configuration to thepumps 10 shown in FIGS. 1 and 2 and FIGS. 7 and 8 so that there is noneed for all features to be described in detail once again, withreference to FIGS. 9 and 10.

The same details are identified in FIGS. 1 through 10 by the samerespective references. FIGS. 1, 3, 5, 7 and 9 also show a pump casing73.

It will be appreciated that the invention is not limited to theconfigurations illustrated in the drawing of the electric drive motorwith a hermetically sealed cooling system 46 whose coolant impeller 48is coupled to the drive shaft 20 of the drive motor 12 by means of apermanent magnet coupling 52.

1. A drive motor, in particular for a pump, comprising: a rotor having adrive shaft, and a stator enclosed by a stator casing which is enclosedby an outer casing, wherein the stator casing and the outer casing forma sealed intermediate space which is statically closed in itself andwhich is filled with a cooling fluid which is positively moved by meansof a coolant impeller, wherein the coolant impeller is coupled to thedrive shaft by means of a permanent magnet coupling.
 2. The drive motoras set forth in claim 1, wherein the permanent magnet coupling is in theform of a synchronous coupling with a first permanent magnet device anda second permanent magnet device which are spaced from each other by agap in which there is provided a partition element of non-magnetisablematerial, wherein the first permanent magnet device is connected to thedrive shaft and the second permanent magnet device is combined with thecoolant impellers.
 3. The drive motor as set forth in claim 2, whereinthe first permanent magnet device is provided in a dry space portion ofthe stator casing, which is sealingly closed by the partition elementand separated from the intermediate space filled with the cooling fluid.4. The drive motor as set forth in claim 2, wherein the first and secondpermanent magnet devices are of a flat-faced disk-shaped configurationand are in the form of face rotational coupling elements axially spacedfrom each other, and that the partition element provided in the axialflat gap between the first and second permanent magnet devices is in theform of a plate element which is fixed sealingly to the stator casing.5. The drive motor as set forth in claim 2, wherein the first and secondpermanent magnet devices are of an annular configuration and arrangedconcentrically relative to each other are in the form of a centralcoupling element.
 6. The drive motor as set forth in claim 5, whereinthe partition element provided in the radial annular gap between thefirst and second permanent magnet devices is in the form of a cup whichis fixed sealingly to the stator casing.
 7. The drive motor as set forthin claim 2, wherein the partition element provided in the radial annulargap between the first and second permanent magnet devices and is in theform of a cylindrical sleeve which is fixed sealingly to the statorcasing.
 8. The drive motor as set forth in claim 1, wherein thepermanent magnet coupling in the form of a hysteresis coupling with apermanent magnet device and a hysteresis surface element comprises amagnetic material of relatively high remanence and relatively lowcoercive field strength, which are spaced by a gap in which there isprovided a partition element of a non-magnetisable material, wherein thehysteresis surface element is connected to the drive shaft or combinedwith a coolant impeller and the permanent magnet device is combined withthe coolant impeller or is connected to the drive shaft.
 9. The drivemotor as set forth in claim 8, wherein the hysteresis surface element isprovided in a dry space portion of the stator casing, which is sealinglyclosed by the partition element and is spatially separated from theintermediate space which is filled with the cooling fluid.
 10. The drivemotor as set forth in claim 8, wherein the hysteresis surface elementand the permanent magnet device are in the form of face rotationalcoupling elements of a flat-faced disk-shaped configuration in mutuallyaxially spaced relationship, and that the partition element provided inthe axial flat gap between the hysteresis surface element and thepermanent magnet device is in the form of a plate element which is fixedsealingly to the stator casing.
 11. The drive motor as set forth inclaim 8, wherein the hysteresis surface element and the permanent magnetdevice are of an annular configuration and are in the form of centralcoupling elements in concentrically arranged relationship.
 12. The drivemotor as set forth in claim 11, wherein the partition element providedin the radial annular gap between the hysteresis surface element and thepermanent magnet device is in the form of a cup which is fixed sealinglyto the stator casing.
 13. The drive motor as set forth in claim 11,wherein the partition element provided in the radial annular gap betweenthe hysteresis surface element and the permanent magnet device is in theform of a cylindrical sleeve which is fixed sealingly to the statorcasing.
 14. The drive motor as set forth in claim 1, wherein thepermanent magnet coupling is in the form of an eddy current couplingwith a permanent magnet device and an eddy current surface element witha surface element facing towards the permanent magnet device andcomprising electrically conductive material and a surface elementprovided at the rear side thereof which faces away from the permanentmagnet device and comprising a soft-magnetic material, which are fixedlyconnected together, wherein the permanent magnet device and the eddycurrent surface element are spaced from each other by a gap in whichthere is provided a partition element of a non-magnetisable material.15. The drive motor as set forth in claim 14, wherein the eddy currentsurface element is provided in a dry space portion of the stator casing,which is sealingly closed by the partition element and separated fromthe intermediate space which is filled with the cooling fluid.
 16. Thedrive motor as set forth in claim 14, wherein the eddy current surfaceelement and the permanent magnet device are of a flat-faced disk-shapedconfiguration and are in the form of face rotational coupling elementsin mutually axially spaced relationship, and that the partition elementprovided in the axial flat gap between the eddy current surface elementand the permanent magnet device is in the form of a plate element whichis fixed sealingly to the stator casing.
 17. The drive motor as setforth in claim 14, wherein the eddy current surface element and thepermanent magnet device are of an annular configuration and arranged inmutually concentric relationship are in the form of central couplingelements.
 18. The drive motor as set forth in claim 17, wherein thepartition element provided in the radial annular gap between the eddycurrent surface element and the permanent magnet device is in the formof a cup which is fixed sealingly to the stator casing.
 19. The drivemotor as set forth in claim 17, wherein the partition element providedin the radial annular gap between the eddy current surface element andthe permanent magnet device is in the form of a cylindrical sleeve whichis fixed sealingly to the stator casing.
 20. The drive motor as setforth in claim 1, wherein the stator casing and/or the outer casingis/are formed with cooling ribs which project into the hermeticallysealed intermediate space which is filled with the cooling fluid. 21.The drive motor as set forth in claim 1, wherein the permanent magnetcoupling with the coolant impeller is provided on the drive shaftbetween the rotor and the pump impeller.
 22. The drive motor as setforth in claim 1, wherein the permanent magnet coupling with the coolantimpeller is provided on a portion of the drive shaft, which is remotefrom the pump impeller.